Thinking about a mini-split...

hotwirez · 07-22-12, 09:52 PM

Long time listener, first time caller, yada, yada...

I have a 2500 sqft Cape Cod style house with in wall radiant heat and no central AC. We're getting by with window units, but I'm starting to get sick of lugging them out of the basement every year and remembering to turn off the dining room unit if I want to use the toaster oven.

I've been looking/thinking of installing ducted mini-splits. I don't really care for the look of wall hang units, and the second floor of the house doesn't have much vertical wall space. What it does have is knee-wall space along the front and back of the house, unfortunately interrupted by dormers on both north and south side. The west side of the house has a bedroom on the second floor, our master bedroom on the first, along with a TV room and half of a 24x22 living room. East side includes a 22x16 dining room, 22x18 kitchen and bedroom and sewing room on the second floor.

So, utilizing the knee wall space, I'd be able to conceal 2 ducted units on the south side of the house - one for the living room/tv room and the other for the first bedroom (and perhaps split off for the dormer/hallway). North side knee wall I'd be able to conceal a unit for the Master bedroom. That would take care of that side of the house, and I'd probably be able to get by with a LG 30K BTU tri-zone unit. I'd have to do a separate (33k) outdoor unit for the east side of the house. Using the knee wall space, I'd be able to conceal units for the kitchen, dining room second bedroom and probably duct off for the sewing room. Added bonus, I could run a fourth unit for the garage so I wouldn't roast/freeze when I work out there.

Naturally, finding any info on the concealed duct units is a little difficult, and what I do find usually shows the concealed units being placed in drop ceiling or other locations. Problem with the knee wall space is that it is not insulated very well - so, during the summer it gets hot and during the winter it gets chilly. I would use properly insulated flexible air delivery tubing/vent stuff, but should I be concerned with the high/low temperatures affecting either the units themselves or the quality of the air being delivered? Is there an issue using the concealed duct units in this way?

Would I be better off biting the bullet and just using the wall hang units?

I've also read varying reviews on the LG units, though more recent stuff appears to be more positive. They have an attractive price, but should I be looking at other manufacturers?

Thanks,
John

S-F · 07-23-12, 04:42 AM

A cape is a very difficult design to deal with from a thermal envelope point of view. Putting mechanicals in unconditioned space is never ideal but often done.

hotwirez · 08-06-13, 09:44 AM

So, I just finished up my Fujitsu AOU36RLXFZ triple zone install (concealed duct). Thanks to many of the threads on here, I *think* I was able to do an outstanding job for about half of what various contractors wanted to charge me.

Downstairs master bedroom has a 9K unit, as does the upstairs kids room. The living room and tv room are cooled by a 12k unit. Each unit has less than 10 feet of total duct work.

I was able to complete the job in a little over two months - working 6 hours each Sunday (kids, family, etc).

This is only half the house though; I get to do the entire thing over again next summer.

jeff5may · 08-06-13, 10:45 AM

Great job! You should save some money heating in the winter vs. straight electric radiant also.

hotwirez · 08-06-13, 11:46 AM

Quote:

Originally Posted by jeff5may

Great job! You should save some money heating in the winter vs. straight electric radiant also.

Actually, our radiant heat is NG based.

jeff5may · 08-07-13, 06:32 AM

OOPS, My mistake. It may or may not save you money during the winter in that case. Since the fracking craze hit, natural gas prices have plummeted. Even though the mini-split unit is most likely 5X as efficient as your radiant heaters, it still might cost more to run.

Daox · 08-07-13, 07:59 AM

Looks good Hotwirez. I like seeing the mastic on the duct joints! That REALLY helped me in my house, my ducting was horrible.

hikerjohnson · 08-20-13, 01:39 PM

Nice looking job!

WyrTwister · 09-28-13, 03:55 PM

Quote:

Originally Posted by hotwirez

So, I just finished up my Fujitsu AOU36RLXFZ triple zone install (concealed duct). Thanks to many of the threads on here, I *think* I was able to do an outstanding job for about half of what various contractors wanted to charge me.

Downstairs master bedroom has a 9K unit, as does the upstairs kids room. The living room and tv room are cooled by a 12k unit. Each unit has less than 10 feet of total duct work.

I was able to complete the job in a little over two months - working 6 hours each Sunday (kids, family, etc).

This is only half the house though; I get to do the entire thing over again next summer.

When I installed our single zone 12,000 BTU mini split , I insulated all but the last foot or so of the two copper lines . To facilitate using the flaring tool .

Boy , did they sweat ! :-(

Insulated them a week or two latter , up to and including the service valves .

God bless
Wyr

hotwirez · 07-14-14, 08:49 AM

...And I got the second part of the house finished this weekend. It's been a long year. Installed a Fujitsu 36K outdoor unit with two 12k indoor concealed duct units, and one 9k unit.

Due to the design of my house, I had to put the condenser about 13 feet off the ground above our kitchen door.

Not the best location for servicing, but a ladder jack and a ramp make it do-able.

Placed two 12k units in the knee-wall space above the kitchen. One is for the kitchen and the other is for the 3rd bedroom upstairs and the hallway.

Again, I'd thank everyone on this board for sharing their MS knowledge - it made the job a lot easier.

07-22-12, 09:52 PM	#1
hotwirez Lurking Renovator Join Date: Jul 2012 Location: Ohio Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	Thinking about a mini-split... Long time listener, first time caller, yada, yada... I have a 2500 sqft Cape Cod style house with in wall radiant heat and no central AC. We're getting by with window units, but I'm starting to get sick of lugging them out of the basement every year and remembering to turn off the dining room unit if I want to use the toaster oven. I've been looking/thinking of installing ducted mini-splits. I don't really care for the look of wall hang units, and the second floor of the house doesn't have much vertical wall space. What it does have is knee-wall space along the front and back of the house, unfortunately interrupted by dormers on both north and south side. The west side of the house has a bedroom on the second floor, our master bedroom on the first, along with a TV room and half of a 24x22 living room. East side includes a 22x16 dining room, 22x18 kitchen and bedroom and sewing room on the second floor. So, utilizing the knee wall space, I'd be able to conceal 2 ducted units on the south side of the house - one for the living room/tv room and the other for the first bedroom (and perhaps split off for the dormer/hallway). North side knee wall I'd be able to conceal a unit for the Master bedroom. That would take care of that side of the house, and I'd probably be able to get by with a LG 30K BTU tri-zone unit. I'd have to do a separate (33k) outdoor unit for the east side of the house. Using the knee wall space, I'd be able to conceal units for the kitchen, dining room second bedroom and probably duct off for the sewing room. Added bonus, I could run a fourth unit for the garage so I wouldn't roast/freeze when I work out there. Naturally, finding any info on the concealed duct units is a little difficult, and what I do find usually shows the concealed units being placed in drop ceiling or other locations. Problem with the knee wall space is that it is not insulated very well - so, during the summer it gets hot and during the winter it gets chilly. I would use properly insulated flexible air delivery tubing/vent stuff, but should I be concerned with the high/low temperatures affecting either the units themselves or the quality of the air being delivered? Is there an issue using the concealed duct units in this way? Would I be better off biting the bullet and just using the wall hang units? I've also read varying reviews on the LG units, though more recent stuff appears to be more positive. They have an attractive price, but should I be looking at other manufacturers? Thanks, John

08-07-13, 06:32 AM	#6
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	OOPS, My mistake. It may or may not save you money during the winter in that case. Since the fracking craze hit, natural gas prices have plummeted. Even though the mini-split unit is most likely 5X as efficient as your radiant heaters, it still might cost more to run. Last edited by jeff5may; 08-07-13 at 06:38 AM..

08-07-13, 07:59 AM	#7
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Looks good Hotwirez. I like seeing the mastic on the duct joints! That REALLY helped me in my house, my ducting was horrible. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

08-06-13, 09:44 AM	#3
hotwirez Lurking Renovator Join Date: Jul 2012 Location: Ohio Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	So, I just finished up my Fujitsu AOU36RLXFZ triple zone install (concealed duct). Thanks to many of the threads on here, I think I was able to do an outstanding job for about half of what various contractors wanted to charge me. Downstairs master bedroom has a 9K unit, as does the upstairs kids room. The living room and tv room are cooled by a 12k unit. Each unit has less than 10 feet of total duct work. I was able to complete the job in a little over two months - working 6 hours each Sunday (kids, family, etc). This is only half the house though; I get to do the entire thing over again next summer.

08-06-13, 10:45 AM	#4
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	Great job! You should save some money heating in the winter vs. straight electric radiant also.

08-20-13, 01:39 PM	#8
hikerjohnson Submarine Renovator Join Date: Jul 2013 Location: Southern Maine Posts: 35 Thanks: 4 Thanked 5 Times in 5 Posts	Nice looking job!

07-14-14, 08:49 AM	#10
hotwirez Lurking Renovator Join Date: Jul 2012 Location: Ohio Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	...And I got the second part of the house finished this weekend. It's been a long year. Installed a Fujitsu 36K outdoor unit with two 12k indoor concealed duct units, and one 9k unit. Due to the design of my house, I had to put the condenser about 13 feet off the ground above our kitchen door. Not the best location for servicing, but a ladder jack and a ramp make it do-able. Placed two 12k units in the knee-wall space above the kitchen. One is for the kitchen and the other is for the 3rd bedroom upstairs and the hallway. Again, I'd thank everyone on this board for sharing their MS knowledge - it made the job a lot easier.